The contra-rotating mechanism means a mechanism in which when a master shaft rotates by a driving source, a slave shaft coaxial with a master shaft rotates in a reverse direction with respect to a master shaft. The CONTRA-rotating mechanism is widely used in the field such as a cooling fan, a blowing fan, a ship, an aircraft or others.
For example, a ship propelling apparatus called a CRP (Contra/Contra Rotating Propeller) is equipped with two propellers which are arranged coaxially and have opposed rotation directions. The ship propelling apparatus makes it possible to enhance energy efficiency while reducing noises with the aid of fluid dynamics of a front propeller and a rear propeller.
The conventional CRP ship propelling apparatus has one dual shaft formed of two shafts which are rotatably inserted. As two motors rotate in opposed directions, two propellers connected to the motors rotate in opposed directions. In the above conventional CRP ship propelling apparatus, since two motors are installed, the construction is complicated, and the area of installation disadvantageously increases, which leads to increasing costs.
The U.S. Pat. No. 5,890,938 discloses an apparatus for reversing the rotations of two shafts from each other by using one motor with the aid of bevel gears. The above apparatus has a complicated construction and is unstable.
The Korean patent number 10-0673560 filed by the same applicant as the present invention discloses an apparatus in which a plurality of intermediate gears are arranged at a front side and a rear side of a panel. In this case, since the number of intermediate gears is a lot, the construction of the apparatus is complicated, the whole volume of the apparatus increases. Since a lot of movements occur at the master shaft and the slave shaft, the mechanism becomes unstable.